A guest at a Blackpool hotel was seen hitting his girlfriend in their bedroom by a night porter.
Unemployed Andrew Watts, 31, of Hollybank Road, Birmingham, pleaded guilty to assault.
Adrian Hollamby, prosecuting, said the couple were staying at the Colonial Hotel on the Promenade on May 2.
A night porter saw Watts outside their room asking to be let in and eventually he was.
The porter then heard a commotion in the room and saw Watts swing his arm at his girlfriend, connecting with either her arm or face. Watts had suffered a cut to his nose.
The victim did not make a formal complaint to police.
Michael Woosnam, defending, said his client could not remember specifically what had happened, except that there had been a running argument between them that evening.
He accepted what the porter had seen.
Watts was fined £100 with £85 costs and ordered to pay a £150 court charge plus £20 victims’ surcharge by Blackpool magistrates.